Electrochemical cells wherein the electrolyte is a gel electrolyte are known, particularly electrochemical cells working on the base of lithium ions circulation in the electrolyte between the electrodes. In such electrochemical cells, it is advantageous to use a gel electrolyte instead of a liquid electrolyte or a solid polymer electrolyte, compared to the use of a liquid electrolyte because a gel electrolyte has no free liquid, and the absence of free liquid guaranties a higher safety while maintaining a high ionic conductivity. It is also advantageous compared to a solid polymer electrolyte, because a gel electrolyte is more flexible than a polymer electrolyte and allows easier processing.
Methods are known for preparing an electrochemical cell comprising a lithium anode, a cathode and a gel electrolyte, which method comprises stacking an anode film, a separator and a cathode film, inserting the assembled elements in a plastic metal bag which is then sealed, injecting an electrolyte composition into the assembled cell, sealing the plastic metal bag. The electrolyte composition comprises a crosslinkable polymer which is crosslinked after sealing the plastic metal bag. According to US 2007/0111105 (Zaghib et al.), crosslinking is promoted by irradiation via an electron beam or by a thermoinitiator. According to WO 2004/045007 (Zaghib et al.), crosslinking of the polymer in the electrolyte composition is carried on by heat treatment at 80° C.
In any case, the prior art methods for the preparation of an electrochemical cell having a gel electrolyte request a heat treatment and/or addition of an initiator to obtain a gel electrolyte from a liquid electrolyte.